# what are these grey rocks in my humidifier?

**URL:** <https://boards.straightdope.com/t/what-are-these-grey-rocks-in-my-humidifier/615372>\
**Category:** Factual Questions\
**Created:** [March 10, 2012, 7:01am UTC](https://boards.straightdope.com/t/what-are-these-grey-rocks-in-my-humidifier/615372 "2012-03-10T07:01:49Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![wolfman](https://avatars.discourse-cdn.com/v4/letter/w/a8b319/32.png) [@wolfman](https://boards.straightdope.com/u/wolfman)\
**Post date:** [March 10, 2012, 7:01am UTC](https://boards.straightdope.com/t/what-are-these-grey-rocks-in-my-humidifier/615372/1 "2012-03-10T07:01:49Z")

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I have a basic steam humidifier I use when i get stuffy. Living in Michigan it seems that the water is full of minerals that turn into these little grey stones in the thing pretty damn quickly for the amount of water boiled off. Like maybe 10-12 1/4 by 1/4 by 1/16 inch rocks I have throw away. Just a bit curious if anybody knows exactly what minerals they are, that form stones that fast?

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [March 10, 2012, 9:01am UTC](https://boards.straightdope.com/t/what-are-these-grey-rocks-in-my-humidifier/615372/2 "2012-03-10T09:01:45Z")

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Most probably dissolved limestone - if instead the water was dripping from your ceiling for a thousand years, you’d get a stalactite.

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**Author:** ![VOW](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/vow/32/3043_2.png) [@VOW](https://boards.straightdope.com/u/VOW)\
**Post date:** [March 10, 2012, 4:16pm UTC](https://boards.straightdope.com/t/what-are-these-grey-rocks-in-my-humidifier/615372/3 "2012-03-10T16:16:32Z")

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If you are gathering rocks in your humidifier, chances are the mist the machine makes is also throwing a fine dust all over the room as well.

Clean everything out with white vinegar, rinse thoroughly, and only use filtered water.  
~VOW

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**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\
**Post date:** [March 10, 2012, 4:34pm UTC](https://boards.straightdope.com/t/what-are-these-grey-rocks-in-my-humidifier/615372/4 "2012-03-10T16:34:23Z")

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steam machines tend to leave the minerals in or on the machine. water with white vinegar will clean.

cold impeller machine are the ones that spew.